usb: dwc2: gadget: ensure lx_state corresponds to current state

usb: dwc2: gadget: ensure lx_state corresponds to current state

Correctly update lx_state on gadget connection and disconnection.
When usb cable is disconnected, lx_state must be updated to L3 as
controller could be in power off state.
When usb cable is connected, lx_state must be updated to L0 as
controller is powered.

Signed-off-by: Gregory Herrero <gregory.herrero@intel.com>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@intel.com>
Tested-by: Robert Baldyga <r.baldyga@samsung.com>
Tested-by: Dinh Nguyen <dinguyen@opensource.altera.com>
Tested-by: John Youn <johnyoun@synopsys.com>
Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>